Tuning for higher base fuel pressure
 

I am currently running PTE 880s with e85 at 18psi, and I am getting high IDCs. Is it acceptable to raise fuel pressure to take some of the work off the injectors? I am running a 255 pump, and I was only flowing around 170 lph while my injectors were maxing out.

From my understanding, If I were to run, say, 50 psi, I would have to decrease global by about 15% (1-sqrt(50/37.5)=-.15) Are there any other factors I would have to worry about, such as changing deadtime or MAFcomp?

Re: Tuning for higher base fuel pressure
 

This is exsactly what I did when I first switched to E85. My 850s at 100% duty cycle at 480 HP uncorected on a dyno dynamics. I used that same formula to adjust for fuel pressure. I dont think I did anything with deadtime but the higher fuel pressure might rais it a little but probly not enuf to change anything. MAFcomp shouldnt change.

Re: Tuning for higher base fuel pressure
 

Just make sure your fuel flow (volume) is acceptable at the higher baseline pressure. As fuel pressure increases, fuel pump volume decreases and if you are in fact at the limit of your pump AND your injectors, you will be pissing into the wind.

Re: Tuning for higher base fuel pressure
 

having same issue but it dont matter what i have for base pressure car runs the same ... ? 37to 55 psi it dont really change. runs lean think the pump is dying its a 255 i get 12.5 to 13.5 in boost but i don't run it or use boost at this time cause of the afrs are too high im on gas right now for safety reasons only a year old pump ?

Re: Tuning for higher base fuel pressure
 

It could be, I would check your fuel pressure under boost and your wide band at the same time. Does the car run like its going lean and into knock retard?

As said above if you raise your base fuel pressure and your fuel pressure drops with boost/rpm or you injector duty cycle stays high you might be on a 2+ front wall, and that is no fun, ask the Axis.

~John

Re: Tuning for higher base fuel pressure
 

Sounds like you need bigger injectors, if you have a 1g the base fuel pressure for e85 is 37psi, adding more fuel will really do nothing since your injectors are maxed. I might waste more fuel if anything.

Re: Tuning for higher base fuel pressure
 

so on to fuel .. i have a single 255 in the tank im wondering if i got the aeromotive stealth pump 340lph would that just be good or do i just get a bosh 044 run it inline with my 255 ?
upping my feed line to -8 for e85

Re: Tuning for higher base fuel pressure
 

Raising the baseline fuel pressure increases the size of the injector, assuming the fuel pump volume is adequate and the injector spray pattern is sufficient. I've been using that trick for 10 years now when the injectors are correctly sized, just the idc's are higher than I'd like, and I have enough fuel pump volume to compensate for the increased fuel pressure. Typically when your baselines get over 50psi and you are running more than 20psi, you really see diminishing gains.

Factory fuel pressure is 36-38psi, most I've seen are around 36psi, but anyone running E85, larger injectors, and a stock fuel pressure regulator, is an idiot. This is because the stock regulator is hardly adequate to control a basic drop in fuel pump, let alone a hardwired Walbro 255hp or anything larger.

Most injectors flow (as well as fuel pumps) advertised levels at 43psi fuel pressure, unless noted elsewhere.

Re: Tuning for higher base fuel pressure
 

well my 255 is hard wired and still outa fuel at 15 psi boost . i turned it back down to 40 psi still goes up to 13.2 and still unsure on the pump i should get it sounds like 2x 255s are still not enough for 500-600 hp on e85 ..

again im getting a tune here for e85 in a month or so and shooting for 400+ hp until i get my new head done thinking about getting an intake made from john gota pm him about it

Re: Tuning for higher base fuel pressure
 

What are the IDC's on your 880's? Sounds like your pump isn't keeping up, is the pick-up sock clogged? I would think a single walbro could come close to supporting 400whp on E85 dependant upon the BSFC of the engine.

Re: Tuning for higher base fuel pressure
 

Are 850s large injectors? Cause iam running them on e85 and hardwire 255 pump with stock fpr. Seems to work just fine for me.

Re: Tuning for higher base fuel pressure
 

Brad (C3l1ca) used the stock FPR making ~600awhp at DB, on e85. (He can chime in with more facts).

Re: Tuning for higher base fuel pressure
 

Not for E85

Re: Tuning for higher base fuel pressure
 

my buddy made a point to check the fuel filter says it might be clogged ? but if that was the case wouldn't it not start . it takes a min for it to start like crank for like 15 sec then it starts i can hear the pump in the tank as usual.

Im going to run a meter to see what im getting for voltage for everything up front.. And see if the relocation of the battery had anything to do with it running 4 gage from the bat to starter then 8 for main harness and patched to to the starter

my idcs are 90-105 on gas right now its undriveable on e85 i dont even boost it right now again all fuel and air settings are maxed past 3500 it dose not make a difference what i do for base pressure but run leaner when i turn it down .

Re: Tuning for higher base fuel pressure
 

Deff change your fuel filter if it's been a while. E-85 is notorious for cleaning out your fuel system and dumping it in your filter

Re: Tuning for higher base fuel pressure
 

Why increase fuel pressure to 43.5 when you are pushing the limits of your injectors? Why not just get bigger injectors and do it correctly instead of half assing it and taking risks on blowing up your motor that you have probably already spent to much on?

And 880's on a stock FPR is pretty stupid 93gtpeater, you should have bought a AFPR before you spent any money on injectors. I'll bet there is a cloud of black smoke behind your car every time you accelerate it's probably running so damn rich. Please tell me you are running dsmlink or something and are not on a stock ecu considering you don't even have an AFPR.

Re: Tuning for higher base fuel pressure
 

43.5psi is the factory flow rating and what they baseline fuel pressure should be.